If you have three minutes, you’ve got to watch this video. Inspiring and artfully done, it depicts world champion and double world record holding freediver William Trubridge freediving. In the narration, William mentions the effects of deep ocean pressure, which can cause nitrogen narcosis. Although we dedicate a lot of our time educating on freediver blackout – commonly referred to as “shallow water blackout” – it’s good to study other impairments from diving that can lead to serious injury.
Nitrogen narcosis is a neurological impairment caused by dissolved blood nitrogen under pressure. The progressive signs and symptoms of nitrogen narcosis are:
- Impairment of reasoning, judgement, memory and concentration;
- Sense of well-being and levity;
- Loss of coordination and physical dexterity;
- Hallucination, terror and vertigo;
- Unconsciousness and death.
The onset of symptoms may start around 100 feet (30 metres) and unconsciousness may occur at around 300 feet (90 metres).
While most of us aren’t freediving down to 300 feet, we can become disoriented and experience impaired judgement which may lead us to stay underwater longer than we should, heightening our risk for freediver blackout.
In reading the 2006 Breath-hold Symposium some time ago, I was captivated by a presentation by Tanya Streeter in which she narrated her No Limits dive to 525 ft. Later, I watched it on video and even though I knew the outcome, it was hard to watch her struggle to remember how to pull the pin that would allow her to ascend from such a great depth. Tanya was clearly confused over how to complete a simple task. Obviously, this type of confusion that can result from competitive deep freediving isn’t something many of us are going to experience, yet it’s important to understand as much about the physiological nuances of our sport as we can.